performance_schema -> information_schema (#6418)

[ti-chi-bot]

This is an automated cherry-pick of #6418

This page mistakenly claimed that statements_summary was in performance_schema rather than information_schema. I also added additional clarification about the difference.

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: ece62a9